Direct Selection For Yield Research Articles

Genetic and phenotypic characterization of Tinopiro (Thinopyrum intermedium) as a dual-purpose perennial crop in the Southern Cone: Doctoral thesis abstract

Agriculture based on annual crops requires intensive input management, which has been associated with significant degradation of natural resources. The development of perennial grain crops such as intermediate wheatgrass - (Thinopyrum intermedium) may greatly contribute to reduce this problem, however, previous research has been carried out in high latitude environments and there is no information on this crop for temperate regions with mild winters. The aims of this thesis were a) to determine the cold requirements of intermediate wheatgrass, b) to evaluate the agronomic performance of intermediate wheatgrass managed as a dual-purpose crop in Uruguay, c) to understand the genetic architecture of grain and forage yield components in intermediate wheatgrass under dual-purpose management. Three experiments were carried out, the first one in growth chambers and the other two in the field during two years in Paysandú, Uruguay. Flowering percentage and most grain yield components increased as the length of the cold incubation period at 5°C and 10 h photoperiod increased from 3 to 7 weeks. High intra-population phenotypic diversity was estimated. The effects of two populations produced under contrasting environments and the effects of three doses of nitrogen on grain and forage yield under dual-purpose management were evaluated in the second experiment. The first year, both populations had similar flowering percentages of about 48%, which resulted in an average grain yield of 316 kg ha -1. The average forage yield for the first year was 14695 kg ha -1 and decreased to 4037 kg ha -1 the second year. Fertilization with 160 kg ha -1 nitrogen increased grain yield by 63% and forage yield by 28%. In the third experiment, grain yield components, forage and phenological traits were evaluated in 30 half-sib families. Most of the traits evaluated showed no genotype x age interaction. Indirect selection for spikes per plant and/or yield per spike could have a greater response to selection than direct selection for yield per plant. No trade-off was detected between grain yield components and aboveground biomass production. These results suggest that expansion of this species as a dual-purpose crop to temperate regions with mild winters is feasible after some cycles of selection.

Evaluation of Relative Efficiency of Several Selection Indices for Prediction of Expected Genetic Advance in Bread Wheat Grain Yield (Triticum aestivum L)

This experiment was conducted with fifteen genotypes of bread wheat introduced from ICARDA and two local varieties (Sham6 and Abu-Graib3), using three rows spacing (15, 25 and 35 cm). All genotypes were grown in 7 December, 2017 at Field Crops farm (inside Mosul University) under rain fed conditions with complementary irrigation, using split plots in randomized complete block design with three replications, for evaluation through constructing several selection indices and calculation of the expected gains of grain yield. The analysis of variance results for studied traits (grain yield, plant height, number spikes, biological yield, number of grains per spike, 1000-grain weight and harvest index) showed that mean square of genotypes were highly significant for plant height, number of grains per spike and 1000 grain weight. The selection index constructed from number of grains per spike and harvest index had high increase in the efficiency as compared with direct selection for yield. This indicate of the importance of a selection index based on combination of characters. This index in the present study considered the superior due to its highest efficiency. Using this index for genotypes evaluation revealed that the higher mean of selection index was 109.961 for genotype REYNA-12 with significant difference over Abu-Graib3 and is not with others, followed in importance by Sham6, ATTILA-7, PASTOR-2/BOCRO-2 and HUBARA-5/3/SHA3/SERI//SHA4LLIRA. The local varieties of bread wheat included in this study, (Sham6 and Abu-Graib3) locates at the sequences 2 and 17 respectively.
 

Nitrogen isotope discrimination in open-pollinated and hybrid canola suggests indirect selection for enhanced ammonium utilization.

Nitrogen isotope discrimination (Δ15N) may have utility as an indicator of nitrogen use in plants. A simple Δ15N-based isotope mass balance (IMB) model has been proposed to provide estimates of efflux/influx (E/I) ratios across root plasma membranes, the proportion of inorganic nitrogen assimilation in roots (P root) and translocation of inorganic nitrogen to shoots (Ti/Tt) under steady-state conditions. We used the IMB model to investigate whether direct selection for yield in canola (Brassica napus L.) has resulted in indirect selection in traits related to nitrogen use. We selected 23 canola lines developed from 1942 to 2017, including open-pollinated (OP) lines developed prior to 2005 as well as more recent commercial hybrids (CH), and in three separate experiments grew them under hydroponic conditions in a greenhouse with either 0.5 mM ammonium, 0.5 mM nitrate, or 5 mM nitrate. Across all lines, E/I, Proot and Ti/Tt averaged 0.09±0.03, 0.82±0.05 and 0.23±0.06 in the low nitrate experiment, and 0.31±0.06, 0.71±0.07 and 0.42±0.12 in the high nitrate experiment, respectively. In contrast, in the ammonium experiment average E/I was 0.40±0.05 while Ti/Tt averaged 0.07±0.04 and Proot averaged 0.97±0.02. Although there were few consistent differences between OP and CH under nitrate nutrition, commercial hybrids were collectively better able to utilize ammonium as their sole nitrogen source, demonstrating significantly greater overall biomass and a lower Proot and a higher Ti/Tt, suggesting a somewhat greater flux of ammonium to the shoot. Average root and whole-plant Δ15N were also slightly higher in CH lines, suggesting a small increase in E/I. An increased ability to tolerate and/or utilize ammonium in modern canola hybrids may have arisen under intensive mono-cropping.

Genetic Diversity and Correlation Coefficient Studies in Muskmelon (Cucumis melo L.)

Background: Genetic diversity provides opportunity for plant breeders to develop new and improved cultivars with desirable characteristics, which include both farmer-preferred traits (yield potential and large seed, etc.) and breeder preferred traits (pest and disease resistance and photosensitivity, etc.). Yield being a complex quantitative character, direct selection for yield may not result in successful improvement. Information on character association and direct and indirect effects of component traits on yield would greatly help in formulating the selection criteria and using them effectively in crop improvement programme. Therefore present study was aimed to evaluate genetic diversity in 25 muskmelon genotypes. Methods: 25 muskmelon genotypes were evaluated at Dr. Y.S.R Horticultural University, College of Horticulture, Anantharajupeta, during 2017-2018 in randomized block design with three replications. Genetic diversity among genotypes was estimated using Mahalanobis D2 statistics. Result: Cluster analysis revealed distinctive clustering pattern and grouped the genotypes in to seven clusters. cluster II was the largest comprising of eight genotypes, while cluster III, IV, VI, VII consist of only one genotype. Cluster VII and IV were found to be considerably different from the rest of the clusters. Genotypes falling in these clusters which are genetically more diverse, can be exploited in a hybridization programmes. Genetic variability in terms of correlation analysis were studied for yield and yield attributing traits. Fruit yield had a positive correlation with fruit volume, fruit diameter, number of fruits per plant, fruit weight and flesh thickness. While it had a negative correlation with days to appearance of first pistillate flower and days to first fruit harvest.

Character Association and Path Analysis for Yield Components and Biochemical Traits in Maize (Zea mays L.) Genotypes

Background: Grain yield is a complex character so direct selection for yield as such can be misleading. Keeping in view, the present study aimed to assess the path coefficient analysis with correlation coefficient technique to establish the direct and indirect relationship between the yield and its component. Methods: The present investigation carried out during kharif 2019 at Centurion University of Technology and Management, Odisha in randomized complete block design with 3 replication involving 20 maize genotypes. Data were collected from five randomly selected plnts on 20 agromorphic and biochemical traits. All the biochemical analysis estimated from leaf sample following standard procedure. Result: The traits shelled grain weight, cob diameter, number of grains per cob and anthesis silking interval were found to possess significant association in disirable direction with five ear weight at both genotypic and phenotypic levels. None of the biochemical trairts establishing significant positive association with yield. Highest positive direct effect on 5 ear weight was noticed by shelled grain weight (1.108) followed by phenols (0.115), internodal length (0.106) and days to 50 percent anthesis (0.102) indicating that the selection for these characters were likely to bring about an overall improvement in grain yield directly.

Evaluation of advanced back cross lines for drought tolerance in rice (Oryza sativa L.)

Drought is the largest abiotic constraint to rice production which cause significant yield loss depending upon the severity. Development of rice varieties with tolerance to drought and high use water use efficiency is the need of the hour. Despite the importance of drought as major abiotic constraint, the efforts to develop drought tolerant rice varieties are very low. Breeding efforts until recent past were focused on understanding and improvement of secondary traits that are putatively associated with drought tolerance. However, the genetic gain in yield by improvement of secondary traits is very low. Hence, improvement of yield per se under drought conditions will be better solution. Introgression of yield QTLs under drought in the genetic background of high yielding varieties will be helpful to overcome the problem to a certain extent. In the present study, 31 advanced back cross lines (BILs) derived from drought susceptible mega variety Samba Mahsuri (BT 5204) and a drought tolerant tolerant land race Azucena were evaluated under drought. Thirty one advanced back cross inbred lines (BC2F4) lines having yield QTLs viz., qDTY3.1 on chromosome 3 and qDTY2.1 on chromosome 2 were phenotyped under drought conditions. The results suggested that wide range of variation was observed for yield and its component traits in the BILs generated in the background of BPT 5204 and direct selection for yield under water stress coupled with marker assisted screening would help in development of drought tolerant version of mega varieties with improved yield under stress. Thermo tolerance studies indicated that high variability was observed for the BILs in terms of % seedling survival, % reduction in root and shoot growth under stress.

Evaluation of Genetic Parameters for Yield and Related Traits in new Recombinants interspecific Mungbean × Mashbean Genotypes

Seventy two Mungbean × Mashbean recombinant genotypes were evaluated in the field for seed yield and its components traits. Highly significant differences were observed among the genotypes. The magnitudes of genotypic and phenotypic coefficients of variability ranged from 2.73% to 28.97% and 3.46% to 31.95%, respectively. Pods per plant exhibited maximum amount of genetic variability followed by clusters per plant and seed yield per plant. 100-seed weight was observed to be the most heritable trait with greatest magnitude (h2 = 99%). Pods per plant had maximum positive and significant genotypic (rg = 0.90) and phenotypic (rp = 0.86) correlations with clusters per plant. Both traits were identified as the most important characters as they had strong genetic and phenotypic relationships with seed yield. Selection for number of pods per plant among different agronomic traits showed greatest improvement in seed yield that was 54% of the improvement possible through direct selection for seed yield. Likewise, clusters per plant and plant height also showed higher improvement in seed yield through indirect selection which was 29% and 20% of the improvement possible by direct selection for yield. Days to flowering also showed promise for 8% of the improvement in seed yield possible through direct selection for seed yield. Thirty six promising recombinants were selected on the basis of desirability index. On the basis of overall performance seven recombinant genotypes, viz; MMH 1115, MMH 4224, MMH 4255, MMH 7124, MMH 2112, MMH 4295 and MMH 2225 were selected as elite lines.

Factors responsible for yield improvement in new Gossypium hirsutum L. cotton cultivars

The factors responsible for yield progress can be analysed through yield determinant frameworks. These conceptual models consider factors such as crop growth dynamics, partitioning of vegetative and reproductive biomass and yield components to provide insights into the factors responsible for observed genetic gains and opportunities for future gains. The aim of this study was to use direct cultivar comparison to assess the rate of genetic gain in the CSIRO (Australia) cotton breeding program, and to understand how factors within a conceptual yield determinant framework relate to yield performance. Using field experimentation, yield progress of 16.1 kg lint ha−1 y−1 was observed in ten cultivars released between 1968 and 2012. This study identified that selection pressure has resulted in improvements in total dry matter (TDM), harvest index (HI), lint percentage and carbon assimilation. While gains have been made in these four parameters, improvements in lint yield have largely been driven by altering HI through increasing lint percentage. Although improvements have been made in TDM, the reproductive allocation of total biomass and the amount and efficiency of light capture has not been altered in modern cultivars. Future gains in lint yield will require the concurrent maintenance of harvest index while producing larger plants with more fruiting branches that capture more incident radiation with increased efficiency. As the collection of phenotype data such as biomass, boll number, boll size and radiation use efficiency at the scale required in a commercial breeding program is largely aspirational, we conclude in the short term improvements may be achieved through direct selection for yield. Future efforts should be placed in increasing early season growth rates, and in the longer term enhancing carbon assimilation rates. Importantly, due to trait associations and the effects of trade-offs between functional components, factors within a conceptual framework must not be considered in isolation.

Sorghum Hybrids for Low‐Input Farming Systems in West Africa: Quantitative Genetic Parameters to Guide Hybrid Breeding

ABSTRACTThe development of sorghum [Sorghum bicolor (L.) Moench] hybrids with Guinea‐race parents is a promising approach to increase yields in West Africa (WA). There is heretofore no quantitative genetic information about the genetic value of new hybrids and their parents, or about the efficiency of alternative selection methods for targeting yield performance under the predominantly low‐input, P‐deficient production conditions. This study aims to estimate the heterosis levels attainable by new Guinea‐race hybrids and the combining abilities of the current suite of parents with partial‐ to full‐Guinea‐race backgrounds of contrasting geographic origins, and to determine the effectiveness of direct selection under low‐P (LP) relative to indirect selection under high‐P (HP) conditions. Single‐cross hybrids were evaluated in 2015 and 2016 for yield under both LP and HP conditions at two locations in Mali. The hybrid yields were substantially superior to farmers’ local Guinea‐race varieties, with 20 to 80% higher means in both LP and HP environments. Average midparent and better‐parent heterosis estimates were, respectively, 78 and 48% under HP, and 75 and 42% under LP. Direct selection for yield under LP was predicted to be 20 to 60% more effective than indirect selection under HP conditions. The combining ability estimates provided initial insights into the potential benefit of germplasm from more eastern and humid regions of WA for developing a restorer pool distinct and complementary to the female pool from Mali and surrounding countries. Substantial yield superiorities of hybrids over local varieties suggested that a hybrid breeding strategy based on Guinea germplasm could help improve WA smallholder farmers’ livelihood.

Stress tolerance indices based on yield, phenology and biomass partitioning: A review

Breeding for water stress tolerance is very difficult as the stress conditions created in experimental set up and actual field conditions, invariably, have poor correspondence. Direct selection for yield under stress holds promise but is slow on account of complexity of yield. Screening based on yield suffers from low heritability. Yield has been the primary breeding objective in production breeding and has been improved either by targeting yield per se as well as yield components based on correlated response. Drought stress indices are quantitative measures that characterize water stress response by yield data from one or several environments based on timing, duration and intensity of stress. Such an index is more readily useable than raw yield data. Since drought resistance is a yield based trait, selection could vary depending on which index is chosen by the breeder. A major drawback of using these indices has been lack of correspondence in rankings across indices and their failure to discriminate overlapping responses in terms of yield under stress. There has been substantial effort on part of scientists to develop and validated different indices based on yield per se, index scores, regression analysis as well as various model based approaches. The major focus has been on identifying variables such as phenology, physiological traits, biomass partitioning or other parameters that influence crop performance under stress. The paper appraises the approaches from yield based indices to regression based as well as crop model based that have been used to understand crop response to water stress.

Selection for water-soluble carbohydrate accumulation and investigation of genetic×environment interactions in an elite wheat breeding population.

Water-soluble carbohydrate accumulation can be selected in wheat breeding programs with consideration of genetic×environmental interactions and relationships with other important characteristics such as relative maturity and nitrogen concentration, although the correlation between WSC traits and grain yield is low and inconsistent. The potential to increase the genetic capacity for water-soluble carbohydrate (WSC) accumulation is an opportunity to improve the drought tolerance capability of rainfed wheat varieties, particularly in environments where terminal drought is a significant constraint to wheat production. A population of elite breeding germplasm was characterized to investigate the potential for selection of improved WSC concentration and total amount in water deficit and well-watered environments. Accumulation of WSC involves complex interactions with other traits and the environment. For both WSC concentration (WSCC) and total WSC per area (WSCA), strong genotype×environment interactions were reflected in the clear grouping of experiments into well-watered and water deficit environment clusters. Genetic correlations between experiments were high within clusters. Heritability for WSCC was larger than for WSCA, and significant associations were observed in both well-watered and water deficit experiment clusters between the WSC traits and nitrogen concentration, tillering, grains per m2, and grain size. However, correlations between grain yield and WSCC or WSCA were weak and variable, suggesting that selection for these traits is not a better strategy for improving yield under drought than direct selection for yield.

Selection of Drought Tolerant Maize Hybrids Using Path Coefficient Analysis and Selection Index.

In drought-prone environments, direct selection for yield is not adequate because of the variable environment and genotype x environment interaction. Therefore, the use of secondary traits in addition to yield has been suggested. The relative usefulness of secondary traits as indirect selection criteria for maize grain yield is determined by the magnitudes of their genetic variance, heritability and genetic correlation with the grain yield. Forty eight testcross hybrids derived from lines with different genetic background and geographical origins plus 7 checks were evaluated in both well-watered and water-stressed conditions over two years for grain yield and secondary traits to determine the most appropriate secondary traits and select drought tolerant hybrids. Study found that broad-sense heritability of grain yield and Ear Per Plant (EPP) increased under drought stress. Ear aspect (EASP) and ear height (EHT) had larger correlation coefficients and direct effect on grain yield but in opposite direction, negative and positive respectively. Traits like, EPP, Tassel Size (TS) and Plant Recovery (PR) contributed to increase yield via EASP by a large negative indirect effect. Under drought stress, EHT had positive and high direct effect and negative indirect effect via plant height on grain yield indicating that the ratio between ear and plant heights (R-EPH) was associated to grain yield. Path coefficient analysis showed that traits EPP, TS, PR, EASP, R-EPH were important secondary traits in the present experiment. These traits were used in a selection index to classify hybrids according to their performance under drought. The selection procedure included also a Relative Decrease in Yield (RDY) index. Some secondary traits reported as significant selection criteria for selection under drought stress were not finally established in the present study. This is because the relationship between grain and secondary traits can be affected by various factors including germplasm, environment and applied statistical analysis. Therefore, different traits and selection procedure should be applied in the selection process of drought tolerant genotypes for diverse genetic materials and growing conditions.

Towards intra-population improvement of alfalfa yield and persistence

Alfalfa (Medicago sativa L.) is the most important forage crop in the world, regarding growing area and economic value, because of its high yield level, good persistence, high protein content and energy value. In alfalfa, concept of intra-population breeding means direct selection for yield, through recurrent phenotypic selection using some form of progeny testing. Significant differences between genotypes were found for green forage and dry matter yields. The observed variation for both yield traits was much higher at population level than for the selected plants that will form new improved population. In the next steps of breeding process selected plants will be intercrossed in isolation to develop a new, improved population. Alfalfa breeding programs should focus on yield per se, with the use of old and new knowledge on the genetic control of yield and with adaptation of existing or developing new breeding procedure.

Selection of barley advanced lines at rainfed conditions using regression and cluster analyses

Due to the low heritability, direct selection for yield has usually low efficiency at rainfed conditions. Therefore, plant breeders may improve yield indirectly through selection of yield contributing traits. The purpose of this study was to suggest a method for indirect selection of promising lines through yield contributing traits. This method was tested on a set of 18 advanced lines of winter barley cultivated at Gachsaran Agricultural Rainfed Research Station, Iran, for two years from 2009-10 to 2010-2011. The experimental design was a randomized complete block with four replications. Grain yield along with eight yield-related traits were assayed. In this method, initially, yield contributing traits were detected using a multiple linear regression analysis. Then, the obtained predictors were weighted by the corresponding regression coefficients. Selection of lines was carried out based on cluster analysis. Estimation of correlation coefficients revealed that, grain yield (GY) was positively correlated with plant height, weight of hectoliter and the number of grains per spike (GS). The highest and lowest broad-sense heritability belonged to GS and GY, respectively. Cluster analysis determined that, genotypes 7-B-Gachsaran, 8-BNYT-Gachsaran and 12B-Gonbad had the best level of yield predictors in both years and therefore, were the most stable genotypes.

Partitioning coefficient—A trait that contributes to drought tolerance in chickpea

Chickpea is increasingly being grown in tropical areas, and terminal drought is becoming a major constraint to its increased productivity. A trait-based selection approach can achieve further gains in drought tolerance that has been achieved through direct selection for yield. Separation of yield into its components including the rate of partitioning and its duration could permit a better focus on the most relevant trait for yield enhancement under terminal drought. Current work is aimed at understanding the importance of rate of partitioning or the partitioning coefficient (p) as a major contributory trait associated with drought tolerance both in germplasm and breeding lines. A reference collection of chickpea germplasm (n=280) was evaluated in the field under both terminal drought and optimally irrigated environments; and a set of desi (n=60) and kabuli (n=60) advanced breeding lines under terminal drought. Grain yield was associated with its analytical components – crop growth rate (C), reproductive duration (Dr) and p. The path analysis showed that C and p had a large direct positive contribution to yield while Dr had a marginal but negative contribution to yield under drought. The direct contribution of p was the highest but it was marginally reduced by the indirect negative contributions of Dr. However, the total contributions of p to grain yield remained large. The yield of germplasm accessions under drought across the seasons were closely associated (r2=0.70) and also the genotype×year interaction was minimum. The contribution of C, Dr and p to grain yield were similar in the advanced breeding lines. However, kabuli breeding lines had a larger variation for p than the desi lines. The results suggest that a conscious selection for greater p will confer greater tolerance to abiotic stresses, given that terminal drought tends to curtail the length of the reproductive period.

Assessment of yield based selection under managed field stress condition for breeding for rice yield improvement under drought

The progress in development and dissemination of drought tolerant lines has been slow as compared to the increasing drought prevalence in the rice growing regions. Significant amount of work has been done in the past on drought resistance traits in rice crop, still the benefit of improved drought tolerant rice cultivars reaching the farmer’s field is not very high and ways to expedite the development of drought tolerant and productive rice cultivars needs to be addressed. In this article, an assessment of easily practicable approach of managed stress screening and prospect of direct selection for yield under drought stress is discussed. Also the large effect yield QTLs identified for grain yield under drought stress field conditions is being reviewed for successful introgression into elite genetic background for developing drought tolerant cultivars with improved yield for the drought prone target environment.

Recent approaches in screening methodology for drought resistance.

Abstract Genetic progress in yield of staple crops is an urgent need in view of population growth. Predicted climate changes due to global warming necessitate that this progress is materialized in environments, which are affected more often by drought. Direct selection for yield under drought conditions is usually hampered by low heritability. Therefore, breeders rely on secondary traits with higher heritabilities to improve drought tolerance in agricultural crops. The present review gives an overview of methods that are applied for screening secondary traits. While for aboveground traits simple, reliable, fast, non-destructive and cost-effective methods that allow a high-throughput phenotyping are available, a bottleneck in drought research methods exists in the root zone, although there is evidence that roots are a key trait for superior drought avoidance. Still only few field screening techniques exist and most root screening is restricted to young plants and artificial growth media that limit inference to field grown adult plants. Spectral methods are identified as promising approach for both above- and belowground measurements and could bridge the gap between high throughput needs of breeding and complexity of plant physiological measurements.

Indirect and Direct Selection for Yield in Coffea canephora Genotypes Under Drought-Stress and Non-stress Conditions

It is a normal practice to select coffee in non-drought-stress environments for use in drought-stress and non-stress conditions. This study assesses the efficiencies of drought stress and non-stress selection environments to improve coffee for adaptability. In a nine-year experiment, 18 genotypes were tested simultaneously under drought-stress and non-stress conditions. Six traits related to Robusta coffee adaptation were evaluated to determine the best environment for improvement and traits amenable to selection for broad adaptation to drought stress. Drought-stress significantly reduced fruit set, fruit/node, number of primary branches, and yields. Span, girth, and diameter of primary branches were not reduced by stress. Genetic correlations between the environments were significant for all the traits (rG = 0.47–0.84) except fruit/node and number of primary branches. Selection of genotypes with broad adaptation to water-deficit stress should be possible through an index including span, girth, diameter of primary branches, fruit set, and yield itself. Lower genotypic and environmental variation coefficients but higher genetic variances and broad-sense heritabilities were observed under non-stress than under stress conditions. Correlated response to selection as against response to selection under stress (0.02–0.90) and non-stress (0.03–0.93) was lower than unity for all the traits. Hence, direct selection of genotypes is predicted to be more efficient in the environments in which they are intended to be used rather than in indirect selection. However, when resources are limited, it is better to select under non-stress conditions.

Genetic basis of variation for lint color, yield, and quality in cotton (Gossypium hirsutum L.)

Colored cotton produces naturally colored lint, which can help reduce the use of toxic dyes in textile. Four naturally colored lint accessions were crossed with eight white lint varieties of Gossypium hirsutum L. to study the genetic basis of variation of lint color, fiber yield, and quality traits. Various shades of lint appeared in the F1 progenies and the inheritance of lint colors appeared to be controlled by dominant genes with varying degrees of dominance. There was also some indication for the involvement of maternal effects in the manifestation of lint colors. Additive and dominance genetic effects were involved in the inheritance of fiber traits, dominance effects being greater. The estimate of narrow sense heritability was very low for seed cotton yield and therefore direct selection for yield would not be effective in isolating superior genotypes. As non‐additive gene effects predominated in the inheritance of most fiber yield and quality characters, the development of colored cotton hybrids and recurrent crossing and selection would be useful for the genetic improvement of colored cottons.

Adaptation strategy, germplasm type and adaptive traits for field pea improvement in Italy based on variety responses across climatically contrasting environments

A pea breeding strategy is required to cope with the large climatic variation featuring south-European environments. Thirty-seven recent cultivars bred by 21 European or Australian institutions were grown in two climatically contrasting Italian sites (Lodi, subcontinental; Foggia, Mediterranean), two cropping years per site and two sowing times per year, to define various elements of this strategy. The study assessed: (i) the impact of genotype × environment (GE) interaction due to spatial and temporal factors on the consistency of top-yielding cultivars; (ii) the similarity between environments for GE effects and its implications on adaptation strategies; (iii) the extent of genotypic and GE interaction effects, and the relationship with adaptive responses, for various morphophysiological traits; (iv) the adaptation pattern and the combination of adaptive traits featuring three germplasm types, i.e. European spring and winter types, and germplasm selected in Mediterranean environments; (v) the predicted efficiency of direct and indirect selection procedures for grain yield. The geoclimatic area had a major impact on crop yield (5.15 t/ha in Lodi vs. 2.52 t/ha in Foggia) but tended to affect GE interaction less than time or year of autumn sowing, suggesting to breed for wide adaptation. Top-yielding cultivars as modeled by additive main effects and multiplicative interaction were environment-specific. On average, spring and winter materials outyielded the Mediterranean germplasm but the spring type, characterized by wide entry variation, included most widely- and specifically-adapted top-yielding cultivars. Cold-tolerant spring-type germplasm is preferable to breed for wide adaptation as it may combine high yield potential with adaptation to winter cold and terminal drought and heat stress. Lodging susceptibility, harvest index, onset and duration of flowering, and canopy height at maturity assessed in individual environments showed moderate to fairly high broad-sense heritability on a plot basis ( h 2 > 0.20) and tended to correlation with yield over test environments ( r ≥ 0.20). An indirect selection index including harvest index and canopy height exhibited about 20% greater predicted efficiency than direct selection for yield when using one selection environment and could be preferred for early selection stages. Direct yield selection in late selection stages should ideally be performed across 2 years in two environments that contrast for geoclimatic area and time of autumn sowing.